Hey all, posted a few times a few years ago, just more out of curiosity than anything else. But now I'm designing a traditional RPG with GM narration and all that jazz and have a couple of questions about resolution mechanic I'm thinking of.

Characters have skills( in the D and D sense) that have a die type attached depending on how skilled they are. Much like savage worlds. However instead of rolling against a target number, they roll against another die that is dependent upon the difficulty of the task. tasks that are hard enough to warrant a roll will be rolled against a d6. skills start at a d4.

So a character wants to leap a gorge, and is only of average fitness and strength. They would roll a d4 against the gorges difficulty of a d6, if the players roll is equal or higher to than the d6 they leap over all the alligators or whatever.

So my questions are1. I am not a mathematician, will the maths be there to ensure fairness and scalability over the long run?

2. Is this easy to learn and apply (obviously this would be easy to answer with a playtest, but my game is not at that stage yet)?

Assuming that a tie is not a success, a d4 beats a d20 only 15% of the time. I got this value by comparing the number of successful rolls versus the total number of possibilities. A d4 can only beat a d20 on three rolls: 4, 3, 2. There are twenty possibilities on a d20.

For the d20, you just have to subtract the percentage it loses to the other dice from 95% (-5% to represent a tie). For example, the d20 beats the d4 on sixteen numbers (5 through 20) and ties only on four numbers (1 through 4). That means it beats a d4 80% of the time. This may seem odd because the d4 only wins 15% of the time isntead of 20%, but that's because a d4 can tie on the "defense" four times instead of three times.

At least I hope that's how this probability stuff works. I'm not that great at math and used google to take a crash course in it haha.

Actually, I was part of a game design group that used d4 through d20 as stats for a tabletop wargame. The math wiz ran 10,000 rolls of each die versus another die and we used those statistics to calculate the cost of the dice.

d4 - 2ptsd6 - 3ptsd8 - 4ptsd10 - 6 ptsd12 - 7 ptsd20 - 14 pts

We found that it was pretty well balanced. Tactics and special abilities / traits played a greater role in defeating your foe than the dice did.

Oh... crap. I just remembered we used exploding dice which greatly threw off the odds. From my experience however, both sides rolling dice worked for a tabletop war game, but I don't know about an rpg.

@Luminous I'm a bit of a systems/math twink. One of the things that attracts me to RPG systems is the complex probability and interaction between various rolls and situations. If you ever need any other computations done, let me know.